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Concurrent Host Communication Physical Unit Activation and Deactivation Handling

IP.com Disclosure Number: IPCOM000108717D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 43K

Publishing Venue

IBM

Related People

Manka, R: AUTHOR [+3]

Abstract

A mechanism is described to manage the SNA activation and deactivation of multiple SNA Physical Units (PUs) in one IBM 3174 Establishment Control Unit when an attached Distributed Function Terminal (DFT) has no knowledge of the fact that it may be connected to more than one communications link at the same time.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 78% of the total text.

Concurrent Host Communication Physical Unit Activation and Deactivation Handling

       A mechanism is described to manage the SNA activation and
deactivation of multiple SNA Physical Units (PUs) in one IBM 3174
Establishment Control Unit when an attached Distributed Function
Terminal (DFT) has no knowledge of the fact that it may be connected
to more than one communications link at the same time.

      The 3174-to-DFT interface specifies that the SNA request units
Activate Physical Unit (ACTPU) and Deactivate PU (DACTPU) are to be
passed to the DFT with an identifier that addresses the physical
display rather than a particular Logical Terminal (LT).  In the
Concurrent Host Communication environment that this article relates
to, if one of the hosts were to issue a DACTPU or an ACTPU, the
3174 could not use the standard technique of device notification.
The DFT (not knowing that more than one communications link exists)
would interpret the standard status to mean that all LTs in the DFT
are to have their sessions reset, which is not necessarily true since
other links could be operational.

      The existing function split between the 3174 and the DFT is
such that the DFT does not need to receive an ACTPU before accepting
an Activate Logical Unit (ACTLU). Historically, this was done so that
the 3274 would not have to generate an ACTPU for a DFT that were to
power on after the 3274 had already received an ACTPU.  The existing
DFT interface command for DACTLU c...